Power amplifier



June 23, 1942. G. BARTH POWER AMPLlFIER Filed April 3, 1940 6 5 d m u J l I AIV AIT All'lnm/ HI! 2 5 A. 0 Av\4 Al l. l uf. l .In Alu lf/MII' nl' Al' Il' Al! Al. .vll nl l n All. .In l nl All* I! I .lv l n nl' lll.. 1]'4 Il' lll' n] A I7 Il JH. Rin/Hu. A' All All' nl' Al' LIII' Al! l 5,4.' lll. Il! All' LII. nl' A v Il.' L Le n0 Patented June 23, 1942 anun rowEa AMPLIFIER 'Gustav Barth, Berlin, Germany, assigner to Asiemens Apparate und Maschinen Gesellschaft mit beschrnkter Haltung, Berlin, Germany, a corporation of Germany Application April 3, 1940, Serial No. 327,702 In Germany November 30, 1938' 8 Claims. (Cl. 171-242) This invention relates to an arrangement for adjusting an organ, particularly a control surface or the like in airplanes or seagoing vessels.

In the copending application Serial No. 290,968, filed August 19, 1939, is described an arrangement for automatically adjusting an organ, particularly a control surface in airplanes or seagoing vessels in accordance with instru ments capable of being loaded only to a slight extent, particularly with directional indicators, such as compasses, gym-indicators etc. A According to the above copending applicatie the electrical magnitude transmitted by said instruments is transmitted to a magnetic amplifier arrangement connected to a feed back circuit and is amplified by the amplifier' arrangement in such a manner that the output energy which the amplifier supplies to the current consuming device, for instance, to an electrical directional drive, has such a value as to bring about an adjustment of the organ.

The present invention relates to an improvement in the novel magnetic amplifier provided in the arrangement according to the above copending application. The invention is based on the fact that means are provided in the feed back circuit of the magnetic amplifier so as to influence the amplification factor and that these means are capable of being controlled in accordance with the electrical magnitudes of the output energy.

Further details of the invention will be apparent from the following description taken in connection with the accompanying drawing, in which Figs. 1 and 2 show diagrammatically the magnetic amplifier described in the above copending application.

Fig. 3 shows an embodiment for carrying out the inventive idea with the aid of the feed back controllable by influencing the effective number of turns of the feed back winding.

Fig. 4 shows a further embodiment with a parallel resistance for the feed back winding, controllable by means of the output alternating current.

Fig. 5 shows another embodiment with a resistance lying in series with the feed back and controllable in accordance with the rectified current serving for the feed back.

Fig. 6 shows an embodiment with a resistance regulable by means of a double instrument. Y

Fig. 7 shows an embodiment with a non-linear resistance serving to control the feed back.

Fig. 8 shows an embodiment with a resistance combination serving to control the feed back.

Fig. 9 shows a modification of the arrangement with a resistance combination shown in Fig. 8.

Fig. l0 shows a connection in diagrammatic form of an arrangement with resistance combinations serving to control the feed back.

Before proceeding with the description of the invention the operation of the novel magnetic amplifier disclosed in the above copending application is hereinafter briefly repeated with reference to Figs. l and 2.

In Fig. 1, lI and 2 denote cores consisting of a material of high magnetic permeability, for instance, of an ironnickel alloy. 'I'he two cores are provided each with a winding 3 and I respectively. The two windings 3 and 4 are arranged in series and in series with the current consuming device 5 energized by the alternatingcurrent source 6. In the windings and therefore in the current consuming device 5 flows an alternating current J whose magnitude depends upon the alternating-current resistance of' the` windings. The magnitude of this resistance depends upon the permeability of the two cores in accordance with the working point on the magnetization curve. `On the two cores is arranged a common winding 'l which is traversed by the direct current ie supplied by an impulse transmitter (not shown). The two windings 3 and l are so wound that the voltages induced in the winding 'l by the current flowing in the windings 3 and l annui each other. The direct current flowing in the winding lv produces in both cores magnetic fluxes which displace the working point on the magnetization curve. By displacing the working point the permeability changes according to the magnetization curve and therefore changes the alternating-current resistance of the windings 3 and 4. The alternating-current resistance of these windings depends therefore upon the direct current ie flowing in the winding l and varies with the direct current.

If the output current is plotted against the input current in a diagram for an arrangement according to Fig. 1 without consuming device, the inclination of the tangent on this curve in the working point is to be considered as the steepness of the magnetic amplifier. The amplification factor of the arrangement depends upon this steepness.

In the arrangement according to the above copending application an increase of the amplification factor is attained by the fact that the alternating current flowing in 'the windings 3 and 4 is rectified and is rendered effective in the sense of a self-amplification by the feed back by supplying the alternating current to an additional winding which is allotted to the two cores in the same manner as the winding 'I of Fig. 1. The eiect of this feed back will now be brieiiy explained with reference to Fig. 2 in con' nection with the disclosure of the above cepending application. In Fig. 2 the same parts are denoted by the same reference numerals as in Fig. l. i and 2 denote the cores consisting of a material of high magnetic permeability, 3 and t the windings arranged on these cores and traversed by the alternating current, 5 the current consuming device and e the power source. i designates the winding traversed by the direct current supplied by the directional indicator d.

The alternating current flowing in the windings alternating-current resistance ci the windings r and l in the same manner as above described :tor the effect oi the current ie owing in the winding l. Depending upon the direction of flow or" the current in the rectifier arrangement and upon the direction oi the current owing in the winding l the current in the winding lil produces in the cores i and 2 magnetic iluxesrwhich have both either the same or opposite direction as the fluxes which are produced by the current ie in the winding i, i. e., the fluxes may be either added or subtracted. It is lirst assumed that z`e=0. The current J flowing in the windings 3- It a current ie ows in the winding i' in the direction that the magnetic iiuxes in the cores produced thereby have the same direction as the fluxes which are produced by i, the working point on the magnetization curve is shifted by the effect of the current ie so as to reduce the permeability of the cores and therefore the aiternating-current resistance of the two windings 3 and 4. With decreasing alternating-current resistance J increases, which in turn brings about an increase of i. vTo the increase of i corresponds an increase of the iiux in the cores produced by this current, which increase causes a further decrease oi the permeability, therefore a further decrease of the alternating-current resistances of the windings 3 and i as well as a further ncrease of the current J. Consequently, the current i causes an increase in the eect of the input current z'e in the form of a self-amplication and therefore an increase in the amplication factor.

In this arrangement the feed back is constant. The magnitude of the feed back and therefore the amplification factor cannot assume any high value for the following reason. The resistance of the two windings 3 and d retains always a definite value also in case the Winding l is deenergized, i. e. an alternating current flows in this arrangement also inthis zero position. This zero current Jo produces a magnetic bias and thereby decreases the initial permeability as well as the initial resistance of the windings 3 and l.

This means an undesirable increase in the zero current with increasing number of turns of the winding lwth respect to an arrangement without feed back and at the same time a restriction of the controllable resistance range of the windings 3 and 4, since the smallest resistance value which these windings may assume'is the value for which the two cores i and 2 are completely saturated. Upon these two moments depends the selection oi the magnitude oi the constant feed back.` Y

According to the present invention the steepness ci the characteristic and therefore the ampli'iication factor oi the arrangement are capable oi being iniiuenced by the fact that means are provided in the feed loaclr circuit for automatlcally controlling the yfeed back and that these means are controllable in accordance with the electricai magnitudes of the output energy.

A practical embodiment of the invention is shown in Fig. 3. In this iigure i and i2 denote the two cores, Si l the windings traversed by the alternating current J, 5 the current consuming device, ii the alternatingecurrentsource, i the winding traversed by the input current ie and il the impulse transmitter supplying the input current. The feed vback winding i@ is directly connected on the one hand to the rectifier arrangement t and on the other hand through a slide Contact il. The slide contact ii is operated oy a device l2 which operates according to this embodiment in the form of a measuring mechanism and is traversed by the output alternating current J. The slide contact causes, depending upon its position, more or less turns of the feed back winding it to he traversed by the rectiued alternating current so as to incr-ease more or less the iced back. arrangement may be so designed that for the zero value Jo of the output current no or only a few turns are inserted in the circuit, that with increasing current J the number of the turns inserted increases and that for the maximum value of this current the desired greatest number of feed back windings lie in the vfeed baci; circuit.

The effect of the iced back may be reduced to a minimum for the zero value Jo of the output current Jwhich means that the alternating current Jo owing in the arrangement may he reduced to a value as is desired for an arrangement without feed back. In this manner at the same time the complete controllable resistance range or the windings 3 and d is maintained as in the case of an arrangement without feed back.

In the embodiment shown in Fig. 4 the arrangement oi the parts l to 9 is the same as in Fig. 3 and therefore it is not shown in this figure. In Fig. 4 the feed back winding le is connected to the points a and b of Fig. 3 and the number of turns of the lwindingr I0 is so chosen that for Y 'the maximum value of the output current J the desired maximum feed back is attained. Parallel to this feed back winding is connected a resist- Y ance |'3 whose effective magnitude is controllable with the aid of the slide contact il operated by the device I2. The device l2 is inserted with the terminals c, d in the circuit of the output alternating current J as in the embodiment shown in Fig. 3. In this case the arrangement is, for instancefso designed that for the maximum In this case the value J the slide contact II lies on the free end of the resistance I3 which is so chosen that it is practically ineffective in this case as a shunt for the winding I0, whereas for lthe zero value Jo of the output alternating current J the slide contact II -lies on the opposite end of the resistance I3 and the winding III is thus practically short circuited and therefore the feedback is ineffective.

Instead of the output alternating current J also a current derived from the current J may be used to operate the measuring mechanism which actuates the slide contact. In the embodiment shown in Fig. 5 in which the same parts are denoted by the same numerals as in the preceding figures a direct-current measuring mechanism I5 is provided which is connected to the points a, b of Fig. 4 and lies in parallel relation to the series connection consisting of the feed back winding III and a variable resistance I4. The resistance I4 lies as mentioned above in series with the feed back winding I and is chosen in this case in such a manner that it attains its maximum value for the zero Value Jo of the output alternating current and the desired minimum value for the greatest value of the current J. The measuring mechanism I5 may, of c ourse, also be series-connected with the winding I0 and the resistance I4, i. e., it may directly-be operated by the current serving for the feed back.

Thecontrol of the feed back may be effected as already mentioned above directly in accordance with the output alternating current or indirectly in accordance with the latter by means of a current derived from the output alternating current. According to the invention also an additional impulse transmitter may be provided, by means of which the feed back is controllable by the current supplied by this additional irnpulse transmitter alone or together with the output alternating current. Such an embodiment is shown in Fig. 6, in which I6 denotes a double device which is operated on the one hand by the output alternating current and on the other hand by an additional current iz of an additional impulse transmitter provided as indicated at I1.

In the embodiment'v according to Fig. 5 the regulable resistance I4 presents a variable resistance whose magnitude depends upon the output alternating current J. This dependence is brought about in this embodiment by the electrical mechanical method. In Fig. 7 is shown an embodiment in which this dependence of the series resistance for the feed back Winding upon the output alternating current of the arrangement is brought about by the electrical method only. In series with the winding I0 is connected the non-linear voltage-responsive resistance I8, for instance, a semi-conductor, a semi-conductor combination with blocking layers or the like which is so chosen that according to its resistance-current characteristic the feed back is controlled in the like manner as described above in accordance with the feed back current and therefore with the output current. The nonlinear resistance may also be connected in parallel to the feed back winding I0 in the manner as shown in Fig. 2, in which case depending upon the desired purpose the resistance characteristic is correspondingly chosen. If the regulation of the feed back should be effected in a manner corresponding to the operation of the arrangement according to. Fig. 4, a current conductor, for instance, an incandescent lamp, may be employed as) a current-responsive resistance, Whose resistance is small for small currents and with increasing current intensity increases in such a manner that for small voltages applied to the terminals a and b this non-linear resistanceI forms a small shunt to the feed back winding so that only a very small fraction of the current supplied by the .rectifier arrangement is employed for the feed back, whereas upon the occurrence of high voltages at the terminals a and b the non-linear resistance assumes a great value so that the main portion of the direct current supplied by the arrangement 9 flows through the winding I0.

A particularly advantageous embodiment of the invention is shown in Fig. 8, in'which the rectifier arrangement 20 included in the feed back circuit is formed in a known manner by non-linear resistances. A resistance 2| which may be a non-linear or linear resistance is connected to the alternating-current input terminals g--h of this rectifier arrangement. To explain the operation reference may be had to Fig. 9 which shows a modification of the arrangement as shown in Fig. 8. In Fig. 9, I0 denotes the feed back winding, 20a a non-linear resistance as a substitute for the rectifier arrangement. Parallel to the series-connected winding I0, resistance 20a is arranged the resistance 2| which may be a non-linear or linear resistance. If a relatively low voltage is applied to the terminals g--h and if a selenium rectifier is employed, for instance for the rectification.' the momentary value of the resistance 20a is great, whereasif a relatively high voltage is applied to the terminals g-h the momentary value of this resistance is small. If, for instance, a linear resistance is employed as a parallel resistance 2|, it may, for instance, be so dimensioned, that it is small as compared to the resistance of the seriesconnection consisting of the winding I0 and the resistance 20a for lowA voltages applied to the terminals g-h (i. e. for small output alternating curren-t J, for which the resistance 20a assumes a great value). In this case only a small fraction of the rectified alternating current flows in the feed back winding I0. If, however, the output alternating current is large a high voltage occurs at the terminals g-h, the momentary value of the resistance 20a is small and therefore the resistance of the series connection Winding III-resistance 20 is small with respect to the resistance 2|.

By means of the resistance 2| it is at the same time posssible to equalize in a simple manner the non-uniformities which occur in the case of mass production, for instance, owing to the nonuniformities of the material, for instance, of the core material which presents in the case of highly permeable materials great fluctuations as to the permeability.

By the choice of this resistance, particularly if this resistance is a non-linear resistance, and of the non-linear resistance 20a it is further possible to influence the characteristic of the amplifier-relation between output current and input current-and to adapt it to a great extent to the corresponding purpose. In this case it is, of course, possible to use the invention in a manner other than the above-described, for instance, in such a manner, that in contradistinction to the embodiments previously described the feed back is kept large for small output alternating currents and small for large output alternating currents.

The resistance 2| may, of course, also be regulated by hand or by a particular impulse transmitter, for instance, in a manner described in the preceding embodiments by auxiliary measuring mechanisms. l

A further advantageous modification of the arrangementl shown in Fig. 8 is illustrated in Fig. 10, in which is shown an arrangement, in which a combination of resistances or a plurality of such resistance combinations as shown in Fig. 9 are provided for the control of the feed back. In Fig. 10, iB denotes the feed back winding and 22 a resistance series-connected thereto. A resistance 23 is parallel connected to the series connection of the parts IU and 22. This arrangement represents a resistance combination which is series-connected with the resistance 29a shown as spare resistance for the rectifier arrangement 213 and a parallel resistance 2i is allotted to the series lconnection which consists of the resistance 29a and of the resistance combination formed of the parts Hi, 22 and 23. The resistances 2i, 22, 23 may be non-linear or linear resistances by means of which it is possible to adapt the characteristic f the amplifier to any desired purpose.

What is claimed is:

l. A magnetic amplifier comprising a magnetizable core carryinga pair of windings connected in series opposed relation, a so. .rce of alternating 'current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current flow in said third winding the permeability of said core is decreased thus causing an increase in the output current of said pair of windings, a feed back circuit comprising a 'fourth winding for said core electrically connected to the output of said rectifying means for aiding the eiiect of the third winding in additionally decreasing the permeability of said core in accordance with the output current of said pair of windings, and control means in said feed back circuit traversed by the output current of said rectifying means for modifying the effect of said fourth winding on said core.

2. A magnetic amplifier comprising a magnetizable core carrying a pair of windings connected in series opposed relation, a source of alternating current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current flow in said third winding the permeability of said core is decreased thus causing an increase in the output current of said pair of windings, a feed back winding on said core electrically connected to the output of said rectifying means for aiding the effect of the third winding in additionally decreasing the permeability of said core in accordance with the output current of said pair of windings, and control means traversed by the output current of said rectifying means for automatically modifying the effect of said feed back winding on said core.

3. A magnetic amplier comprising a magnetizable core carrying a pair of windings connected-in series opposed relation, a source of alternating current connected to energize said pair of windings, lmeans for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current flow in said third winding the reactance and output current of said pair of windings is varied, a feed back coil on said core electrically connected with the output of said rectifying means for modifying the reactance of said pair of windings, and means for selecting the edective value of said feed back coil in accordance with the current output ol said pair of windings.

4. A magnetic amplifier comprising a magnetizable core carrying a pair of windings connected in series opposed relation, a source of alternating current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current iiow in said third winding the reactance and output current of said pair of windings is varied, a feed back coil on said core electrically connected with the output of said rectifying means for modifying the reactance of said pair of windings, and means including a slidaeie Contact engaging said feed back coil for selecting the effective value of said coil in accordance with the current output of said pair of windings.

5. A magnetic amplifier comprising a magnetizable core carryinfr a pair of windings connected'in series cpposed relation, a'source of alternating current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current flow in said third windingthe reactance and output current of said pair of windings is varied, a feed back coil on said core electrically connected with the output of said rectiiying means for modifying the reactance of said pair of windings, and means including a resistance in circuit with said coil for controlling the effective value of said coil in accordance with a current derived from the output current of said pair of windings.

6. A magnetic amplifier comprising a magnetizable core carrying a pair of windings connected in series opposed relation, a source of alternating current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current ow in said third winding the reactance and output current of said pair of windings is varied, a feed back coil on said core electrically connected with the output of said rectifying means for modifying the reactance of said pair of windings, a resistor in circuit with said coil, and means including a slidable contact engaging said resistor for controlling the eifective value of said coil as a function of the output current of said pair of windings.

7. A magnetic amplifier comprising a magnetizable core carrying a pair of windings connected in series opposed relation, a source of alternating current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current fiow in said third winding the reactance and output current of said pair of windings is Varied, a feed back coil on said core electrically connected with the output of said rectifying means for modifying the reactance of said pair of windings, and means deiining a non-linear resistance in circuit with said coil for controlling current iiow in said coil in accordance with the output current of said pair of windings.

8. A magnetic amplifier comprising a magnetizable core carrying a pair of windings connected in series opposed relation, a source of alternating current connected to energize said pair of windings, means for rectifying the output current of said windings, a direct current input circuit including a third winding on said core whereby during current flow in said third winding the reactance and output current of said pair of windings is varied, a feed back coil on said core electrically connected with the output of said rectifying means for modifying the reactancevof said pair of windings, and nonlinear resistance means in series with said coil whereby current ow in said coil is controlled in accordance with the output current of said pair of windings.

GUSTAV BARTH. 

